Liquid crystal display device

ABSTRACT

In a picture element ( 100 ), transmissive electrodes ( 130, 140 ) are connected to each other, and reflective electrodes ( 110, 120 ) adjacent to the transmissive electrodes are connected to the transmissive electrodes ( 130, 140 ), respectively. However, the reflective electrodes ( 110, 120 ) are not connected to each other. Alignment controlling structures ( 111, 121, 131, 141 ) are provided in regions which correspond to central parts of the respective electrodes, and an alignment controlling structure ( 151 ) is provided between the reflective electrodes ( 110, 120 ) which are not connected to each other. An alignment of liquid crystals is forcibly made stable in the vicinity of the reflective electrodes by providing the alignment controlling structure ( 151 ). It is thus possible to achieve a transflective liquid crystal display device having an excellent display characteristic, such as less roughness and fewer residual images.

TECHNICAL FIELD

The present invention relates to liquid crystal display devices and, inparticular, to a transflective liquid crystal display device including areflective region where a display is carried out in a reflective modeand a transmissive region where a display is carried out in atransmissive mode.

BACKGROUND ART

Recently, liquid crystal display devices are widely used as displaydevices of personal computers or portable information terminals. Theapparatus such as personal computers or portable information terminalsare often used not only indoors but also outdoors. Accordingly, displaydevices having a high level of visibility both in the indoors andoutdoors are desired. In the outdoors, a user often uses such a displaydevice while doing something else. A display device is thus requiredwhich has a high level of visibility when seen from every direction.

Patent Literature 1 discloses a transflective liquid crystal displaydevice which meets the above-mentioned requirement and has an improvedviewing angle characteristic. FIG. 5 illustrates the transflectiveliquid crystal display device disclosed in Patent Literature 1. (a) ofFIG. 5 is a plan view illustrating a configuration of electrodes in onepicture element region of the transflective liquid crystal displaydevice, and (b) of FIG. 5 is a cross sectional view taken along the line1B-1B′ in (a) of FIG. 5.

In (a) of FIG. 5, a reference numeral 500 denotes one picture element ofthe transflective liquid crystal display device. The one picture element500 includes two reflective regions R and one transmissive region Twhich is sandwiched by the two reflective regions R. Note that a pictureelement is a minimum unit of display, and in accordance with a generalcolor liquid crystal display device, three picture elements whichcorrespond to respective three colors of R, G, and B constitute onepixel. A picture element is also referred to as a sub pixel.

The reflective regions R includes three reflective electrodes 511, 512,and 513 which are (i) circular and (ii) arranged in a lateral direction(see above the transmissive region T in (a) of FIG. 5) and threereflective electrodes 531, 532, and 533 which are (i) circular and (ii)arranged in a lateral direction (see below the transmissive region T in(a) of FIG. 5). The transmissive region T includes three transmissiveelectrodes 521, 522, and 523 which are (i) circular and (ii) arranged ina lateral direction. Any two adjacent ones of the electrodes areconnected to each other via a bridge electrode 510 having a narrow width(in FIG. 5, the reference numeral 510 is given to only one bridgeelectrode in order to prevent the figure from being complicated).Accordingly, in a case where a driving voltage is being applied, thesame driving voltage is applied to all of the reflective electrodes 511,512, and 513, and the transmissive electrodes 521, 522, and 523, and thereflective electrodes 531, 532, and 533.

As is illustrated in (b) of FIG. 5, the reflective electrodes 511, 512,and 513, and the transmissive electrodes 521, 522, and 523, and thereflective electrodes 531, 532, and 533 (i) are provided on an activematrix substrate 541 on which active elements for driving the electrodesare formed, and (ii) face a counter electrode 543 provided on a colorfilter substrate 542 on which color filters are formed. Further, liquidcrystals 550 having negative dielectric constant anisotropy are sealedbetween the active matrix substrate 541 and the counter substrate 542.

In the example illustrated in FIG. 5, protrusions 544 made from atransparent dielectric material are formed in regions, on the colorfilter substrate 542, which correspond to the reflective regions R. Theprotrusions 544 serve to make retardation caused by the liquid crystals550 substantially equivalent in the transmissive region T and thereflective regions R. Note, however, that the detailed description ofthe protrusions 544 will be omitted here.

While a driving voltage is being applied to such a transflective liquidcrystal display device, an electric field in an oblique direction isgenerated on the periphery of each of circular electrodes, whichconstitute one picture element 500. This causes a plurality of liquidcrystal domains to be formed along the electric field in the obliquedirection. In each of the plurality of liquid crystal domains, theliquid crystals are tilted and oriented radially. As the result, it ispossible to provide a transflective liquid crystal display device havingan improved viewing angle characteristic.

Alignment controlling structures which are substantially circular (notillustrated in FIG. 5) can be provided in regions, on the color filtersubstrate, which face the respective central parts of the circularreflective electrodes 511, 512, and 513, the circular transmissiveelectrodes 521, 522, and 523, and the circular reflective electrodes531, 532, and 533. As the alignment controlling structure, a variety ofstructures, typically, a protrusion made from a transparent dielectricmaterial or other materials, can be employed.

According to the technology described in Patent Literature 1, a liquidcrystal display device can be attained, which includes a transmissiveregion T and reflective regions R, and a plurality of liquid crystaldomains in each of which liquid crystals are tilted and orientedradially. It is therefore possible to achieve a transflective liquidcrystal display device which (i) is usable both in the indoors and theoutdoors and (ii) has an excellent viewing angle characteristic.

CITATION LIST Patent Literature

Patent Literature 1

Japanese Patent Application Publication Tokukai No. 2005-250431 A(Publication Date: Sep. 15, 2005)

SUMMARY OF INVENTION Technical Problem

According to the technology described in Patent Literature 1, atransflective liquid crystal display device having an improved viewingangle characteristic can be attained. However, there is a problem thatorientation state of the liquid crystals in the reflective region R isnot always stable, resulting in failing to obtain a transflective liquidcrystal display device having an intended characteristic.

FIG. 6 illustrates why an orientation state of liquid crystals inreflective regions of a conventional transflective liquid crystaldisplay device become unstable, with reference to a solution attained bythe inventors of the present invention.

In FIG. 6, a reference numeral 600 denotes a single picture elementregion. The single picture element region 600 is configured to include(i) two reflective electrodes 610 and 620, and (ii) two transmissiveelectrodes 630 and 640. Further, two adjacent ones of the electrodes areconnected to each other via respective bridge electrodes 651, 652, 653,and 654. In the example of FIG. 6, alignment controlling structures arefurther formed in regions, on the color filter substrate, which face therespective central parts of the electrodes.

Namely, an alignment controlling structure 611 is provided so as to facethe central part of the reflective electrode 610, an alignmentcontrolling structure 621 is provided so as to face the central part ofthe reflective electrode 620, an alignment controlling structure 631 isprovided so as to face the central part of the transmissive electrode630, and an alignment controlling structure 641 is provided so as toface the central part of the transmissive electrode 640. As thealignment controlling structure, a variety of structures, typically, aprotrusion made from a transparent dielectric material or othermaterials, can be employed.

While a voltage is being applied to the bridge electrodes 651, 652, 653,and 654, an oblique electric field is generated on the periphery of thebridge electrodes. This contributes to the orientation of liquid crystalmolecules in an oblique direction. Note, however, that the reflectiveelectrodes 610 and 620 are usually provided with small concavities andconvexities for improvement in the reflection characteristics. This maycause the oblique electric field to compete with the concavities andconvexities of the reflective electrodes, in the bridge electrode 651between the reflective electrodes 610 and 620. This may cause (i) theorientation state of the liquid crystal molecules to be affecteddepending on, for example, how the concavities and convexities areformed and ultimately (ii) the orientation state to be unstable. Incontrast, the transmissive electrodes 630 and 640 have respective flatsurfaces facing the liquid crystals, and there is nothing which affectsthe transmissive electrodes 630 and 640, except for the centralalignment controlling structures 631 and 641 and the bridge electrode653. Accordingly, a stable orientation of the liquid crystal moleculescan be achieved.

The present invention has been accomplished in view of the problem, andan object of the present invention is to provide a transflective liquidcrystal display device which can achieve a stable orientation state ofthe liquid crystal molecules even in a reflective region R.

Solution to Problem

In order to attain the above object, a transflective liquid crystaldisplay device in accordance with the present invention is atransflective liquid crystal display device including: a first substrateon which a plurality of picture element electrodes and driving elementsfor selectively driving the picture element electrodes are provided; anda second substrate on which color filters are formed; and liquidcrystals sealed between the first substrate and the second substrate,each of the plurality of picture element electrodes being constituted by(i) at least one transmissive electrode, (ii) at least one pair of tworeflective electrodes which are adjacent to each other leftward andrightward or upward and downward, and (iii) bridge electrodes via eachof which two adjacent ones of the at least one pair of reflectiveelectrodes and the at least one transmissive electrode are connected toeach other, the at least one pair of two reflective electrodes which areadjacent to each other being not connected to each other via the bridgeelectrode, alignment controlling structures for controlling alignment ofthe liquid crystals being provided in regions, on a second substrateside, which face respective central parts of the at least one pair ofreflective electrodes and the at least one transmissive electrode, analignment controlling structure(s) for controlling alignment of theliquid crystals being further provided in a region, on the secondsubstrate side, which region faces a region, where no bridge electrodeis provided, between the at least one pair of two reflective electrodeswhich are adjacent to each other.

According to the configuration, it is possible to provide atransflective liquid crystal display device which has (i) a stableorientation state of liquid crystals, and (ii) an excellent displaycharacteristic, such as less roughness and fewer residual images.According to the transflective liquid crystal display device of thepresent invention, one picture element includes (i) at least onetransmissive electrode, and (ii) at least one pair of reflectiveelectrode which are adjacent to each other leftward and rightward orupward and downward. This leads to formation of a plurality of liquidcrystal domains. This allows the transflective liquid crystal displaydevice to further have an excellent viewing angle characteristic.

Other objects, features and advantages of the present invention are tobe appreciated with reference to the description below. Further,advantageous effects of the present invention are to be appreciated withreference to the description on the basis of the attached drawings.

Advantageous Effects of Invention

As has been described above, a transflective liquid crystal displaydevice in accordance with the present invention includes: a firstsubstrate on which a plurality of picture element electrodes and drivingelements for selectively driving the picture element electrodes areprovided; and a second substrate on which color filters are formed; andliquid crystals sealed between the first substrate and the secondsubstrate, each of the plurality of picture element electrodes beingconstituted by (i) transmissive electrode, (ii) at least one pair of tworeflective electrodes which are adjacent to each other leftward andrightward or upward and downward, and (iii) bridge electrodes via eachof which two adjacent ones of the at least one pair of reflectiveelectrodes and the at least one transmissive electrode are connected toeach other, the at least one pair of two reflective electrodes which areadjacent to each other being not connected to each other via the bridgeelectrode, alignment controlling structures for controlling alignment ofthe liquid crystals being provided in regions, on a second substrateside, which face respective central parts of the at least one pair ofreflective electrodes and the at least one transmissive electrode, analignment controlling structure(s) for controlling alignment of theliquid crystals being further provided in a region, on the secondsubstrate side, which region faces a region, where no bridge electrodeis provided, between the at least one pair of two reflective electrodeswhich are adjacent to each other.

According to the present invention, it is possible to achieve atransflective liquid crystal display device having (i) an excellentviewing angle characteristic, and (ii) an excellent displaycharacteristic, such as less roughness and fewer residual images.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1

FIG. 1 illustrates a first example of the present invention.

FIG. 2

FIG. 2 illustrates variations of the first example of the presentinvention.

FIG. 3

FIG. 3 illustrates a second example of the present invention.

FIG. 4

FIG. 4 illustrates variations of the second example of the presentinvention.

FIG. 5

FIG. 5 illustrates a conventional technology.

FIG. 6

FIG. 6 is a diagram for explaining a problem in the conventionaltechnology.

DESCRIPTION OF EMBODIMENTS

The following description will discuss embodiments of the presentinvention with reference to the drawings in detail. Note that variouslimitations which is preferable to implement the present invention willbe added to the following description, however, the technical scope ofthe present invention is not limited to the embodiments below andillustrations of the drawings.

Embodiment 1

Embodiment 1 of the present invention will be described with referenceto FIG. 1.

FIG. 1 illustrates a configuration of electrodes provided, on an activematrix substrate side, in one of picture element regions 100(hereinafter, referred to merely as a picture element 100) constitutinga transflective liquid crystal display device in accordance with thepresent invention. On an active matrix substrate, serving as a firstsubstrate, driving elements such as TFTs are formed. The active matrixsubstrate is also referred to as a TFT substrate. A picture element is aminimum unit of a display. With regard to a general color liquid crystaldisplay device, each pixel is constituted by three picture elementswhich correspond to respective three colors of R, G, and B. A pictureelement is also referred to as a sub pixel. On the active matrixsubstrate, a plurality of picture element electrodes are provided sothat each picture element electrode is selectively driven by acorresponding active element (a driving element).

The present specification does not specifically describe a cross-sectionconfiguration of the transflective liquid crystal display device inaccordance with the present invention. However, the transflective liquidcrystal display device can have a cross-section configuration which issimilar to that of the conventional technology illustrated in FIG. 5.Therefore, also in Embodiment 1, liquid crystals are sealed in a gapbetween (i) the picture element electrodes and (ii) a counter electrodeprovided on a color filter substrate (a second substrate) (notillustrated). (a) of FIG. 1 illustrates a state in which no drivingvoltage is applied across the picture element electrodes and the counterelectrode, and (b) of FIG. 1 illustrates how liquid crystal moleculesorient while a driving voltage is being applied across the pictureelement electrodes and the counter electrode. Further, (c) of FIG. 1illustrates a typical alignment controlling structure.

In FIG. 1, the picture element 100 includes a plurality of electrodes onthe active matrix substrate (the first substrate). Specifically, thepicture element 100 includes two reflective electrodes 110 and 120, andtwo transmissive electrodes 130 and 140. An alignment controllingstructure 111 for controlling the alignment of the liquid crystals isprovided in a region, on a color filter substrate (the second substrate)side, which region faces a central part of the reflective electrode 110.An alignment controlling structure 121 for controlling the alignment ofthe liquid crystals is provided in a region, on the color filtersubstrate side, which region faces a central part of the reflectiveelectrode 120. An alignment controlling structure 131 for controllingthe alignment of the liquid crystals is provided in a region, on thecolor filter substrate side, which region faces a central part of thetransmissive electrode 130. An alignment controlling structure 141 forcontrolling the alignment of the liquid crystals is provided in aregion, on the color filter substrate side, which region faces a centralpart of the transmissive electrode 140 (the alignment controllingstructure for controlling the alignment of the liquid crystals beinghereafter referred to as just an alignment controlling structure).

The transmissive electrodes 130 and 140 are connected to each other viaa bridge electrode 156. The transmissive electrode 130 and thereflective electrode 110 are connected to each other via a bridge 155.The transmissive electrode 140 and the reflective electrode 120 areconnected to each other via a bridge electrode 157. Each bridgeelectrode can be the same conductor as a reflective electrode or atransmissive electrode, and can be formed simultaneously with forming ofthe reflective electrode or the transmissive electrode. One pictureelement electrode is constituted by the two reflective electrodes 110and 120, the two transmissive electrodes 130 and 140, and the bridgeelectrodes 155, 156, and 157.

According to Embodiment 1 of the present invention, as illustrated in(a) of FIG. 1, no bridge electrode is provided for connecting thereflective electrode 110 to the reflective electrode 120. Instead, analignment controlling structure 151 is provided in a region, on thecolor filter substrate side, which region faces a region between thereflective electrode 110 and the reflective electrode 120. A protrusionbeing (i) made from a transparent dielectric material and (ii) providedon the counter electrode 163 on the color filter substrate 162 asillustrated in (c) of FIG. 1 can be used as the alignment controllingstructure 151. Note, however, that Embodiment 1 is not limited to this,and therefore any other conventionally known alignment controllingstructure can be employed as the alignment controlling structure 151.

(b) of FIG. 1 shows a state obtained in a case where a driving voltageis being applied across the picture element 100 of (a) of FIG. 1. (b) ofFIG. 1 simply illustrates how the alignment controlling structuresoperate under such a state. In (b) of FIG. 1, arrows 113, 113A, 113B,123, 133, and 143 indicate orientation states of liquid crystalmolecules. Note that not all the arrows have reference numerals so thatthe figure is prevented from being complicated too much. Also note thatblack circle sections with the reference numerals 112, 122, 132, and 142denotes the centers of orientation axes of the respective liquid crystalmolecules (hereinafter, referred to as an orientation axis center).

In regions in which the respective transmissive electrodes 130 and 140are provided, liquid crystal molecules are oriented radially towards theorientation axis centers 132 and 142 located at the central parts of therespective transmissive electrodes 130 and 140 (see the arrows 133 and143). In a region between the reflective electrode 110 and thereflective electrode 120, no bridge is provided, and the alignmentcontrolling structure 151 is provided instead.

In a region where the reflective electrode 110 is provided, due to thealignment controlling structure 151 thus provided, some liquid crystalmolecules are oriented in a direction towards an orientation axis center112 (in a direction of the arrow 113A), whereas some liquid crystalmolecules are oriented in a direction towards an orientation axis center152 (in a direction of an arrow 113B). Note, however, that no unstableorientation state is caused. It would appear that this will be caused byproviding the alignment controlling structure having a strongercapability of alignment controlling than that of the bridge. This isbecause the provision of the alignment controlling structure causes anorientation center to be forcibly generated.

The same applies to a region where the reflective electrode 120 isprovided. Namely, some liquid crystal molecules are oriented in adirection towards an orientation axis center 122, whereas some liquidcrystal molecules are oriented in a direction towards an orientationaxis center 152. Note, however, that this is forcibly caused by thealignment controlling structure 151, and thus no unstable orientationstate is caused. In the other parts of the reflective electrodes 110 and120, liquid crystal molecules are oriented substantially radiallytowards the orientation axis centers 112 and 122 (see the arrows 113 and123), respectively. This makes it possible to provide a transflectiveliquid crystal display device having (i) a stable alignmentcharacteristic, and (ii) an excellent display quality, such as lessroughness, and fewer residual images.

According to Embodiment 1, two reflective electrodes and twotransmissive electrodes are provided, that is, are identical in number,and the transflective liquid crystal display device has a relativelyhigh level of visibility in both indoor and outdoor environments. Withregard to a transflective liquid crystal display device includingrelatively large-sized pixel electrodes, the transflective liquidcrystal display device can attain a more stable alignment of liquidcrystals, and an excellent display quality, such as less roughness andfewer residual images, in a case where two reflective electrodes and twotransmissive electrodes are provided than in a case where one reflectiveelectrode and one transmissive electrode are provided.

(a) and (b) of FIG. 2 illustrate modifications of the transflectiveliquid crystal display device, illustrated in FIG. 1, in accordance withthe present invention. In the modifications illustrated in (a) and (b)of FIG. 2, the number of reflective electrodes is greater than that oftransmissive electrodes. Such modifications are suitable for a liquidcrystal display device which is often used outdoors.

(a) and (b) of FIG. 2 are identical to each other in that a pictureelement 200 includes one transmissive electrode 210 and three reflectiveelectrodes 220, 230, and 240. However, they differ from each other inthat their alignment controlling structures are provided in respectivedifferent regions which are located, on a color filter substrate side,between the two reflective electrodes.

According to the configuration illustrated in (a) of FIG. 2, atransmissive electrode 210 and a reflective electrode 220 are connectedto each other via a bridge electrode 254, the transmissive electrode 210and a reflective electrode 230 are connected to each other via a bridgeelectrode 253, and the reflective electrode 220 and a reflectiveelectrode 240 are connected to each other via a bridge electrode 251. Nobridge electrode is provided between the reflective electrode 230 andthe reflective electrode 240. Instead, an alignment controllingstructure 261 is provided in a region, on the color filter substrateside, which region faces a region between the reflective electrode 230and the reflective electrode 240. The bridge electrode 251 is providedso that a driving voltage is supplied to the reflective electrode 240via the bridge electrode 251. Since the alignment controlling structureis provided “in a region, on the color filter substrate side, whichregion faces a region between the reflective electrode 230 and thereflective electrode 240” as described above, it is possible to providea transflective liquid crystal display device having a more stablealignment characteristic, as compared with a case where a bridgeelectrode is provided between any respective adjacent electrodes.

In (b) of FIG. 2, the reflective electrode 230 and the reflectiveelectrode 240 are connected to each other via a bridge electrode 252.Instead, the reflective electrode 220 and the reflective electrode 240are not connected to each other via a bridge electrode, and an alignmentcontrolling structure 262 is provided in a region, on the color filtersubstrate side, which region faces a region between the reflectiveelectrode 220 and the reflective electrode 240. Also in this case, aswith the case of (a) of FIG. 2, it is possible to provide atransflective liquid crystal display device having a more stablealignment characteristic, as compared with a case where a bridgeelectrode is provided between any respective adjacent electrodes.

According to the modifications illustrated in (a) and (b) of FIG. 2, itis necessary that two reflective electrodes are connected to each othervia a bridge electrode, in order that a driving voltage is applied toall of the electrodes in one picture element. According to atransflective display device including a plurality of reflectiveelectrodes in one picture element, it is possible to attain, as a whole,more improvement in alignment characteristic of the display device, evenin a case where part of the reflective electrodes are connected to eachother via a bridge electrode(s), as compared with a case where a bridgeelectrode is provided between any respective adjacent electrodes. It istherefore possible to provide a transflective liquid crystal displaydevice having an excellent display characteristic.

In a case where (i) a plurality of transmissive electrodes and aplurality of reflective electrodes are provided and (ii) no bridgeelectrode is provided between any two adjacent reflective electrodes, adistance from a feeding point where a driving voltage is supplied to areflective electrode will be long depending on the location of thereflective electrode. In view of the circumstances, it is possible toprovide a bridge electrode(s) between some reflective electrodes. Thisalso leads to a good result from the perspective that electricalconductivity of the electrodes should be secured. In this case, it istherefore possible to reduce the adverse effect caused by the fact thata wire length etc. is lengthened within one picture element. Thefollowing description will discuss Embodiment 2 in which a plurality ofreflective electrodes are provided in one picture element in detail withreference to FIG. 3.

Embodiment 2

FIG. 3 illustrates Embodiment 2 of the present invention. In FIG. 3, areference numeral 300 denotes one picture element. In the pictureelement 300, nine electrodes are provided in a matrix of three lines andthree columns: namely, (i) reflective electrodes 310, 320, and 330 in afirst line; (ii) transmissive electrodes 340, 350, and 360 in a secondline; and (iii) reflective electrodes 370, 380, and 390 in a third line.And, (i) alignment controlling structures 311, 321, and 331 are providedin regions on a color filter side so as to face central parts of therespective reflective electrodes 310, 320, and 330, (ii) alignmentcontrolling structures 341, 351, and 361 are provided in regions on thecolor filter side so as to face the central parts of the respectivetransmissive electrodes 340, 350, and 360, and (iii) alignmentcontrolling structures 371, 381, and 391 are provided in regions on thecolor filter side so as to face the central parts of the respectivereflective electrodes 370, 380, and 390.

The adjacent transmissive electrodes 340 and 350 are connected to eachother via a bridge electrode, and the adjacent transmissive electrodes350 and 360 are connected to each other via a bridge electrode. Further,as illustrated in FIG. 3, the transmissive electrodes 340, 350, and 360are respectively connected to (i) the reflective electrodes 310, 320,and 330 via respective bridge electrodes and (ii) the reflectiveelectrode 370, 380, and 390 via respective bridge electrodes. In thiscase, a picture element electrode of one picture element 300 isconstituted by (i) nine electrodes in total, that is, the reflectiveelectrodes 310, 320, and 330 and the transmissive electrodes 340, 350,and 360, and the reflective electrodes 370, 380, and 390 and (ii) thebridge electrodes each connecting a corresponding transmissive electrodeto a corresponding reflective electrode or corresponding two adjacenttransmissive electrodes, of the nine electrodes.

According to the present invention, any two adjacent ones of thereflective electrodes 310, 320, and 330 are not connected to each other.Similarly, any two adjacent ones of the reflective electrodes 370, 380,and 390 are not connected to each other. Further, as illustrated in FIG.3, (i) an alignment controlling structure 301 is provided in a region,on a color filter substrate side, which region faces a region betweenthe reflective electrode 310 and the reflective electrode 320, (ii) analignment controlling structure 302 is provided in a region, on thecolor filter substrate side, which region faces a region between thereflective electrode 320 and the reflective electrode 330, (iii) analignment controlling structure 303 is provided in a region, on thecolor filter substrate side, which region faces a region between thereflective electrode 370 and the reflective electrode 380, and (iv) analignment controlling structure 304 is provided in a region, on thecolor filter substrate side, which region faces a region between thereflective electrode 380 and the reflective electrode 390. That is,instead of bridge electrodes for connecting adjacent reflectiveelectrodes to each other, the alignment defining structures are providedin regions on the color filter substrate side so as to face regionsbetween the adjacent reflective electrodes.

Note that, in Embodiment 2, (i) a picture element (sub pixel) isconfigured to have a shape of a square whose side is about 250 μm, (ii)each of the reflective electrodes and the transmissive electrodes havinga shape of a square whose side is about 75 μm, and (iii) each of thealignment controlling structures is configured to be a circularstructure with a diameter of about 17 μm. This leads to a positiveoutcome.

As early described, the reflective electrode has a surface on whichconcavities and convexities are provided for improving reflectioncharacteristics, but this may cause an orientation state of liquidcrystal molecules to be unstable. However, in accordance with thepresent invention, liquid crystal molecules are oriented forcibly byproviding alignment controlling structures in regions, on the colorfilter substrate side, which face regions between the adjacentreflective electrodes. This makes an orientation state of the liquidcrystal molecules stable. It is thus possible to achieve a transflectiveliquid crystal display device having an excellent characteristic, suchas less roughness and fewer residual images.

In FIG. 3, the reflective electrodes and the transmissive electrodes arearranged in a lateral direction (leftward and rightward direction).Note, however, that these electrodes can be arranged in a verticaldirection. That is, a picture element can be used which is obtained byrotating, by an angle of 90°, the picture element 300 of FIG. 3clockwise (not specifically illustrated). In this case, a pictureelement electrode is constituted by nine electrodes arranged in a matrixof three lines and three columns. Of the nine electrodes, threeelectrodes in the second column (in the central) are transmissiveelectrodes, three electrodes in the first column and three electrodes inthe third column are reflective electrodes. The locations of thealignment controlling structures are obtained by rotating, by an angleof 90°, the picture element 300 of FIG. 3 clockwise.

Further, in the transflective liquid crystal display device ofEmbodiment 2 of the present invention (see FIG. 3), reflectiveelectrodes and transmissive electrodes which constitute one pictureelement electrode are increased in number as compared with thetransflective liquid crystal display device of Embodiment 1 of thepresent invention (see FIG. 1). In regions of the increased electrodes,domains, in each of which liquid crystal molecules are tilted andorientated radially, are formed. It is thus possible to obtain atransflective liquid crystal display device of Embodiment 2 having (i)an excellent display characteristic, such as less roughness and fewerresidual images, and (ii) an excellent viewing angle characteristic.

As has been described with reference to (a) and (b) of FIG. 2, whichillustrate the transflective liquid crystal display device according tothe variations of Embodiment 1, it is not necessary to provide alignmentcontrolling structures in respective regions, on the color filtersubstrate side, which regions face “regions between the reflectiveelectrodes”, instead of providing bridge electrodes in such regions, inorder to attain an improvement in display quality of the display device,as a whole.

For example, in FIG. 3, even in a case where, instead of the alignmentcontrolling structure 301 provided “in a region, on the color filtersubstrate side, which region faces a region between the reflectiveelectrode 310 and the reflective electrode 320”, “a bridge electrode forconnecting the reflective electrode 310 to the reflective electrode 320”is provided, the alignment characteristics of the display device will besignificantly improved as a whole. Consequently, it is possible toprovide a transflective liquid crystal display device having anexcellent display characteristic, such as less roughness and fewerresidual images. Further, since the transflective liquid crystal displaydevice includes a plurality of reflective electrodes and a plurality oftransmissive electrodes within one picture element, a plurality ofliquid crystal domains will be formed. This brings about a furthereffect of having an excellent viewing angle characteristic.

That is, in a picture element electrode constituted by (i) at least onetransmissive electrode, (ii) at least one pair of “two reflectiveelectrodes which are adjacent to each other” leftward and rightward orupward and downward, and (iii) bridge electrodes each of which connectscorresponding two adjacent ones of the at least one transmissiveelectrode and the at least one pair of reflective electrodes, no bridgeelectrode is provided between “two reflective electrodes which areadjacent to each other”. Instead, an alignment controlling structure isprovided on a color filter substrate side so as to face that region(between the two reflective electrodes which are adjacent to eachother). This allows, as a whole, an improvement in alignmentcharacteristics of liquid crystals of the display device, as comparedwith a display device in which a bridge electrode are connected betweenany adjacent two electrodes, of the reflective electrodes and thetransmissive electrodes.

Note here that “leftward and rightward”, and “upward and downward” mean“leftward and rightward”, and “upward and downward” on a display screenof a liquid crystal display device. An example of a picture elementelectrode including a pair of two reflective electrodes which areadjacent to each other leftward and rightward will be described later,with reference to (e) of FIG. 4.

FIG. 4 illustrates modifications of Embodiment 2 illustrated in FIG. 3.(a) through (d) of FIG. 4 illustrate modifications in which thereflective electrodes and the transmissive electrodes illustrated inFIG. 3 are varied in shape. Note that the electrodes have the sameconfigurations as those of FIG. 3 except for their shapes, and theirdetailed descriptions will be omitted. That is, in accordance with thepresent invention, alignment controlling structures are provided inregions, on a color filter substrate side, which face a region betweenreflective electrodes, and alignment controlling structures are furtherprovided in regions, on the color filter substrate side, whichsubstantially correspond to central parts of the respective electrodes(not illustrated in FIG. 4).

(a) of FIG. 4 illustrates a picture element 410 in which circularelectrodes are provided. (b) of FIG. 4 illustrates a picture element 420in which rectangular electrodes whose corners are rounded are provided.(c) of FIG. 4 illustrates a picture element 430 in which electrodeswhose corners are prong are provided. (d) of FIG. 4 illustrates apicture element 440 in which rhomboid electrodes are provided. Theelectrodes which are circular or whose corners are rounded have animproved alignment stability of liquid crystals in the corners, whereashave deteriorated transmittance due to the corners which are rounded andcircular. The shape of electrodes should be determined in accordancewith a field in which a liquid crystal display device is used.

(e) of FIG. 4 illustrates a picture element including the differentnumbers of reflective electrodes and transmissive electrodes from thoseof (a) through (d) of FIG. 4. In (e) of FIG. 4, a display device isillustrated as an example, which includes, as picture element electrodeswithin one picture element, “a pair of two reflective electrodes whichare adjacent to each other leftward and rightward.” Specifically,according to the example illustrated in (e) of FIG. 4, a picture elementincludes two reflective electrodes and eight transmissive electrodes. Nobridge electrode is provided between the reflective electrodes. Instead,an alignment controlling structure 451 is provided in a region, on acolor filter substrate side, which region corresponds to a regionbetween the reflective electrodes. The liquid crystal display device is(i) designed in view of giving importance to transmittance, and (ii)suitably used as a display device for use in a field in which it is usedmore often indoors than outdoors. Also in this case, in accordance withthe present invention, alignment controlling structures are provided inregions, on the color filter substrate side, which substantiallycorrespond to center parts of the reflective electrodes and thetransmissive electrodes (not illustrated in (e) of FIG. 4).

In each of the examples illustrated in (a) through (d) of FIG. 4, it ispossible to obtain a transflective liquid crystal display device having(i) a stable orientation state of liquid crystals, and (ii) an excellentdisplay characteristic, such as less roughness and fewer residualimages. Furthermore, in the modifications illustrated in (a) through (d)of FIG. 4, the reflective electrodes are twice as many as thetransmissive electrodes. It is therefore possible to provide a liquidcrystal display device which is suitable for outdoor use. Since theliquid crystal display device includes a plurality of reflectiveelectrodes and a plurality of transmissive electrodes, a plurality ofdomains are formed around the respective electrodes. In each of thedomains, liquid crystals are tilted and oriented radially. It istherefore possible to provide a display device having an excellentviewing angle characteristic. In the modification illustrated in (e) ofFIG. 4, the transmissive electrodes are more than three times as many asthe reflective electrodes. The liquid crystal display device is suitablefor indoor use.

The descriptions have discussed (1) a picture element including tworeflective electrodes and two transmissive electrodes (Embodiment 1),(2) a picture element including three reflective electrodes and onetransmissive electrode (a modification of Embodiment 1), (3) a pictureelement including three reflective electrodes and six transmissiveelectrodes (Embodiment 2), and (4) a picture element including tworeflective electrodes and seven transmissive electrodes (a modificationof Embodiment 2). Note, however, that the present invention is notlimited to the picture elements (1) through (4). The present inventionis therefore applicable to, for example, (i) a picture element includingthree reflective electrodes and three transmissive electrodes or (ii) apicture element including more than three reflective electrodes and morethan three transmissive electrodes. In FIG. 3, and (a) through (d) ofFIG. 4, the reflective electrodes and the transmissive electrodes arearranged in lateral directions of the drawings. Note, however, that thedirections are not limited to the lateral direction, and therefore thereflective electrodes and the transmissive electrodes can be arranged invertical directions.

Further, according to the present invention, the alignment controllingstructures are provided only on the color filter side, and no protrusionor the like is provided on an active matrix substrate side. This bringsabout an effect of simplifying the manufacturing process.

Summary of Embodiments

As described above, in order to attain the object, a furthertransflective liquid crystal display device in accordance with thepresent invention is characterized in that each of the picture elementelectrodes is constituted by two reflective electrodes and twotransmissive electrodes.

According to the configuration, a transflective liquid crystal displaydevice having (i) a high level of visibility in both indoor and outdoorenvironments, (ii) a stable orientation state, and (iii) an excellentcharacteristics, such as less roughness and fewer residual images. Sincetwo reflective electrodes and two transmissive electrodes are providedin one picture element, a plurality of liquid crystal domains will begenerated. This brings about an effect of having an excellent viewingangle characteristic. Further, since one picture element includes thesame numbers of the reflective electrodes and the transmissiveelectrodes, it is possible to achieve a transflective liquid crystaldisplay device having relatively high definition.

In order to attain the object, a further transflective liquid crystaldisplay device in accordance with the present invention is characterizedin that each of the picture element electrodes is constituted by nineelectrodes arranged in a matrix of three lines and three columns, andthree electrodes in a second line of the matrix are transmissiveelectrodes, and three electrodes in a first line and three electrodes ina third line are reflective electrodes.

According to the configuration, the reflective electrodes which aretwice as many as the transmissive electrodes are provided. This makes itpossible to achieve a liquid crystal display device suitable for use asa display device of a mobile device or the like which is often usedoutdoors, the liquid crystal display device having (i) a stableorientation state of liquid crystals, and (ii) an excellent displaycharacteristic, such as less roughness and fewer residual images.According to the configuration, the numbers of the reflective electrodesand the transmissive electrodes constituting one picture element areincreased. Domains, in each of which liquid crystals are tilted andoriented radially, are formed around the respective electrodes. Thismakes it possible to achieve a transflective liquid crystal displaydevice having (i) a stable orientation state, (ii) an excellent displaycharacteristic, such as less roughness and fewer residual images, and(iii) an excellent viewing angle characteristic.

In order to attain the object, a further transflective liquid crystaldisplay device in accordance with the present invention is characterizedin that each of the picture element electrodes is constituted by nineelectrodes arranged in a matrix of three lines and three columns, andthree electrodes in a second column of the matrix are transmissiveelectrodes; and three electrodes in a first columns and three electrodesin a third column are reflective electrodes.

According to the configuration, as with the above-described case, thereflective electrodes which are twice as many as the transmissiveelectrodes are provided. This makes it possible to achieve a liquidcrystal display device suitable for use as a display device of a mobiledevice or the like which is often used outdoors, the liquid crystaldisplay device having (i) a stable orientation state of liquid crystals,and (ii) an excellent display characteristic, such as less roughness andfewer residual images. According to the configuration, the numbers ofthe reflective electrodes and the transmissive electrodes constitutingone picture element are increased. Domains, in each of which liquidcrystals are tilted and oriented radially, are formed around therespective electrodes. This makes it possible to achieve a transflectiveliquid crystal display device having (i) a stable orientation state,(ii) an excellent display characteristic, such as less roughness andfewer residual images, and (iii) an excellent viewing anglecharacteristic.

In order to attain the object, a further transflective liquid crystaldisplay device in accordance with the present invention is characterizedin that each of the reflective electrodes and the transmissiveelectrodes, which constitute the picture element electrode, isrectangular. Alternatively, in order to attain the object, a furthertransflective liquid crystal display device in accordance with thepresent invention is characterized in that each of the reflectiveelectrodes and the transmissive electrodes, which constitute the pictureelement electrode, is circular. Alternatively, in order to attain theobject, a further transflective liquid crystal display device inaccordance with the present invention is characterized in that each ofthe reflective electrodes and the transmissive electrodes, whichconstitute the picture element electrode, is rhomboid.

According to the electrodes having the above described shapes, it isalso possible to provide a transflective liquid crystal display devicehaving a stable orientation state and an excellent viewing anglecharacteristic. Further, in a case where the electrode is circular orhas corner sections which are circular, it is possible to achievefurther improvement in alignment stability.

The specific embodiments or examples described in the DetailedDescription of the present invention are to clarify the technicalcontents of the present invention. The present invention is not limitedto the embodiments and should not be interpreted in a narrower sense,and can therefore be modified in many ways within the spirit of thepresent invention and the scope of Claims thereof.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide atransflective liquid crystal display device suitable for use in a mobiledevice or the like which is often used indoors and outdoors, thetransflective liquid crystal display device having an excellent displaycharacteristic, such as less roughness and fewer residual images.Therefore, the present invention has notable industrial applicability.

REFERENCE SIGNS LIST

-   100 Picture element-   110, 120 Reflective electrode-   130, 140 Transmissive electrode-   111, 121, 131, 141, 151 Alignment controlling structure-   112, 122, 132, 142, 152 Orientation axis center-   113, 123, 133, 143 Alignment direction-   155, 156, 157 Bridge electrode-   162 Color filter substrate-   163 Counter electrode-   200 Picture element-   210 Transmissive electrode-   220, 230, 240 Reflective electrode-   251, 252, 253, 254 Bridge electrode-   261, 262 Alignment controlling structure-   300 Picture element-   310, 320, 330, 370, 380, 390 Reflective electrode-   340, 350, 360 Transmissive electrode-   311, 321, 331, 341, 351, 361, 371, 381, 391 Alignment controlling    structure-   410, 420, 430, 440, 450 Picture element-   451 Alignment controlling structure

1. A transflective liquid crystal display device comprising: a firstsubstrate on which a plurality of picture element electrodes and drivingelements for selectively driving the picture element electrodes areprovided; and a second substrate on which color filters are formed; andliquid crystals sealed between the first substrate and the secondsubstrate, each of the plurality of picture element electrodes beingconstituted by (i) at least one transmissive electrode, (ii) at leastone pair of two reflective electrodes which are adjacent to each otherleftward and rightward or upward and downward, and (iii) bridgeelectrodes via each of which two adjacent ones of the at least one pairof reflective electrodes and the at least one transmissive electrode areconnected to each other, the at least one pair of two reflectiveelectrodes which are adjacent to each other being not connected to eachother via the bridge electrode, alignment controlling structures forcontrolling alignment of the liquid crystals being provided in regions,on a second substrate side, which face respective central parts of theat least one pair of reflective electrodes and the at least onetransmissive electrode, an alignment controlling structure(s) forcontrolling alignment of the liquid crystals being further provided in aregion, on the second substrate side, which region faces a region, whereno bridge electrode is provided, between the at least one pair of tworeflective electrodes which are adjacent to each other.
 2. Thetransflective liquid crystal display device as set forth in claim 1,wherein: each of the picture element electrodes is constituted by tworeflective electrodes and two transmissive electrodes.
 3. Thetransflective liquid crystal display device as set forth in claim 1,wherein: each of the picture element electrodes is constituted by nineelectrodes arranged in a matrix of three lines and three columns, andthree electrodes in a second line of the matrix are transmissiveelectrodes, and three electrodes in a first line and three electrodes ina third line are reflective electrodes.
 4. The transflective liquidcrystal display device as set forth in claim 1, wherein: each of thepicture element electrodes is constituted by nine electrodes arranged ina matrix of three lines and three columns, and three electrodes in asecond column of the matrix are transmissive electrodes; and threeelectrodes in a first columns and three electrodes in a third column arereflective electrodes.
 5. The transflective liquid crystal displaydevice as set forth in claim 1, wherein: each of the reflectiveelectrodes and the transmissive electrodes, which constitute the pictureelement electrode, is rectangular.
 6. The transflective liquid crystaldisplay device as set forth in claim 1, wherein: each of the reflectiveelectrodes and the transmissive electrodes, which constitute the pictureelement electrode, is circular.
 7. The transflective liquid crystaldisplay device as set forth in claim 1, wherein: each of the reflectiveelectrodes and the transmissive electrodes, which constitute the pictureelement electrode, is rhomboid.